A Russian cargo ship loaded with refurbished attack helicopters has turned back toward home after having its insurance canceled, British Foreign Secretary William Hague says, according to the BBC.

The MV Alaed was was passing by Scotland's north coast at the time. The policy was canceled by The Standard Club, a London-based insurer. According to the BBC, the insurer issued a statement saying:

"We were informed on Friday evening that the ship might be carrying weapons, in particular attack helicopters, missiles and non-specific munitions, and we are making inquiries to establish what their side of the story is.

"There are exclusion clauses in our cover and, for anyone involved in improper or unlawful trade, we can cancel cover."

The U.S. has been sharply critical of Russia over the issue of the helicopters, which Secretary of State Hillary Rodham Clinton has said would sharply escalate the conflict in Syria. Russia has insisted it is only fulfilling a contract and that it is not supplying Bashar Assad's regime with weapons that can be used against civilians.

Watchdog groups, activists and U.N. officials say more than 10,000 people — most of them civilians — have died in Syria since protests against the Assad regime began there in March 2011. Most of the killing, they say, has been carried out by government forces or militias loyal to Assad.